The Fibula is located on the tibia’s lateral side, with which it’s connected below and above. The Fibula is the smaller of the 2 bones at its length proportion – the most slender of all individual’s long bones.

Fibia’s lower extremity inclines a little forward; it projects below the tibia and forms the ankle joint’s lateral part. Its upper extremity is small and is located toward tibia head’s back, below the knee joints level, and excluded from this joint formation. The upper head of extremity (proximal extremity; capitulum fibula) is a form of irregular quadrate locating above the articular flattened surface, directed medialward, forward and upward, for corresponding articulation surface on the tibia’s lateral condyle. On the lateral side is a rough and thick prominence, that is continuing behind into the Apex (styloid process) – a pointed eminence, directs upward from the posterior head’s area. The prominence at lateral and upper area attaches to the knee-joint’s Fibular collateral ligament (the ligament dividing the tendon in 2 parts) and to the biceps of Femoris tendon. The remaining head’s circumference part is rough for ligaments and muscle attachment. It is located in Peronaeus Longus Anterior fibers and in upper origin of Tubercle; and the surface for the head’s anterior ligament attachment; and behind another tubercle for the upper soleus fibers origin and head’s posterior ligament.

Corpus Fibulae (shaft) or the Body

The body is divided in 4 borders, such as postero-medial, antero-lateral, postero-lateral, and the antero medial; and 4 surfaces-lateral, anterior, medial and posterior.

1. Postero-Medial border, known as Oblique Line, starts above the bone head’s medial side, and finishes by becoming continuous at the 4th bone with the interosseous crest.

2. The Antero-Lateral border starts above the bone head’s front, running downward vertically to a little below at bone’s middle, and after that, curves lateralward, bifurcating so as embracing a subcutaneous triangular surface quickly above the lateral malleolus. Antero-lateral border attaches to the intermuscular septum, which separates the Extensor muscle on the leg’s anterior surface from the Brevis and peronaei longus on the lateral surface.

3. Postero-Lateral border is prominent; it starts above the Apex and finishes below the lateral malleolus’ posterior border. It is directed above lateralward, backward, a little below medialward, and backward in the middle of its course, and attaching to an aponeurosis, separating lateral peronaei surface from the muscles of Flexor on the posterior surfaces.

4 Interosseous or Antero-Medial border is located close to the preceding medial side and running next to parallel with it in the 3rd extent’ upper, but diverging from it in the lower 2/3s. It starts just above the bone’s head beneath and ending at the triangular rough apex surface promptly above the lateral malleolus’ articular facet. It serves for the interosseous membrane attachment, separating the muscle of extensor in front from behind flexor’s muscles.

Surfaces:

1. The Lateral Surface located between postero-lateral and antero-lateral borders. It’s a broad and, is frequently grooved deeply; it’s directed in the lower 3rd backward, lateralward in the upper 2/3rd of its course, where it connects with the lateral malleolus posterior border. The lateral surface gives origin to the brevis and peronaei longus.

2. Anterior Surface is the space between antero-medial and anterio-lateral borders. It’s very flat and narrow in the extents’ upper 3rd; serves for the origin of 3 muscles: Peronaeus Tertius, Extensor Hallucic Longus, and Extensor Digitorum Longus; and grooved and broader in its lower 3rd longitudinally.

3. Medial Surface is the space between the postero-medial and antero-medial borders. It’s grooved for the tibialis posterior origin.

4. Posterior surface is the interval between the postero-medial and postero-lateral borders; it’s continuing below with the triangular part above the lateral malleolus’ articular surface; it’s pointed above backward, medialward and backward at its middle, directly below medialward. Posterior’s Surface third upper is rough for the Soleus origin; its lower part presents a triangular surface, connecting with the tibia by a strong interosseous ligament; the surface intervening portion is covered by the origin fibers of the Halluciss Longus Flexor.

Close to the middle of the Posterior Surface is the Nutrient Foramen, which is directed downward. Lateral malleolus or lower extremity (external malleous, distal extremity, malleolus lateralis) is the pyramidal lower extremity form and is flattened from one side to another; it is continues to a lower level than the medialmalleous. The lateral Surface is subcutaneous, convex and continuing with the subcutaneous, triangular of the body’s lateral side surface. The Medial Surface locating in smooth triangular surface’ front, convex from above downward which is articulating with the talus lateral side surface. Beneath and behind-the articular surface is the rough depression,which attaches to the Talofibular posterior ligament.

The anterior border is rough and thick, and marked below by the depression for Talofibular anterior ligament attachment. Such border is broad and presents the malleolar Sulcus shallow for the brevis and peronaei tendons’ passage. The summit is round and is attaching to the Clacaneofibular ligament.

Ossification

The Fibula is ossified from 3 centers:

1. -For the body and other – for either end. Ossification starts in the body about 8th week of fetal life and extends directly to the extremities. At the child’s birth, the ends are Cartilaginous. Ossification commences in the lower end in the 2nd year, and in approx. 4th year. The first to assify-the lower Epiphysis, unites with the person’s body about the 20th year; the upper Epiphysis unites at about 25 years of age.